Spotify Technology continues to grow its user base, hitting 777 million monthly active users at the end of June-but the cost of wooing and keeping customers is increasing as well.

Its second-quarter operating expenses rose 19% from the prior-year period, excluding payroll tax-related expenses and currency movements.

Spotify cited increased marketing costs, as well as cloud and AI-related spending for new app features. It recently rolled out listener-generated, AI-powered podcasts and is developing an AI tool that lets music fans make remixes and cover songs within the app as a paid add-on.

Shares in Spotify slid about 6% in premarket trading.